Sophie Walker says the Women’s Equality party has 45,000 members and supporters across 65 UK branches.
Photograph: Graeme Robertson/for the Guardian

The leader of the new Women’s Equality party has called for a gender quota system to select MPs at the next two elections to achieve equal representation in the House of Commons by 2025.

Sophie Walker, a former Reuters journalist, is urging her fellow political leaders to sign up to the goal of gender parity in the lower house of parliament within the next decade, as she condemned the “glacial pace of change” in society when it comes to women’s equality.

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She announced the proposal ahead of the party’s policy launch next week, six months after the organisation was founded by the comedian Sandi Toksvig and journalist Catherine Mayer.

The party has spent the last few months in consultation about how to achieve its aims of equality in politics, business, education, pay, parenting and the media, as well as an end to violence against women. It now has 45,000 members and supporters across 65 branches, compared with Ukip’s most recent claim to have “more than 40,000” members and the Green party’s 65,000.

Speaking to the Guardian, Walker said her party had calculated it was possible to reach gender equality among MPs by 2025 by making sure there are all-women shortlists in the former seats of at least two-thirds of retiring MPs.

The Women’s Equality party also wants to see three-quarters of all peerages handed to women in order to have parity in the House of Lords by 2035.

“We are going to come out and say that in order to establish an equal system of politics, we think the time has come to put parliament into special measures,” Walker said. “For the next two elections, we think we need quotas to bring in 50/50 representation. We can do it in two elections.”

Labour has already used all-women shortlists, which has increased the party’s ratio of female MPs to 43%. However, the tactic has always been resisted by the Conservative party, 21% of whose MPs are female, and the Lib Dems, who no longer have any female MPs. About 36% of SNP MPs are women.

However, Labour does not escape criticism from Walker, who said she was disappointed to see the party’s top leadership and shadow cabinet jobs go to men under Jeremy Corbyn. “Labour has made significant progress on taking on all-women shortlists, but what’s happened over the last few weeks has shown us there is a problem in the internal structure of the party when all of the party’s leaders and mayoral candidates are male.”

She welcomed the message of David Cameron’s Conservative party conference speech that he wanted to end discrimination, but said time would tell whether it was genuine. The response of the other leaders to the Women’s Equality party’s proposals is likely to affect where and how it stands candidates at the 2020 election, she said. At the moment, however, the party is focused on choosing candidates for next year’s devolved assembly and council elections.

Addressing traditional criticism that quotas could be unfair on male candidates and unmeritocratic, Walker says: “Which quotas are you referring to? Are you referring to the quotas we are suggesting here, or are you referring the centuries-old, unlegislated quotas that have meant men have had an unfair institutional advantage for centuries? To me, those are quotas – it’s just they are not written down in law. That makes them much more invidious.”

Walker addressed the argument that quotas allow in mediocre people by saying: “A system in which you are fishing in a small pool of people who all look and sound alike is more likely to create mediocrity than if you break it open to the huge diversity in our country. We have 30 million women in the country; I think it’s highly unlikely you would struggle to find 325 brilliant ones to become MPs.”

The party is only proposing gender quotas, but wants to support all groups at a disadvantage in their representation in politics, business and other spheres of life. “We want to represent not just people who are disadvantaged because of their gender, but people who are doubly or trebly or quadruply disadvantaged by their gender, and their race and their socioeconomic background and their age and their disability,” Walker said.

Without quotas, the party believes gender parity in the House of Commons will not be achieved until 2055, and in the House of Lords until 2100.

Meanwhile, a coalition of civil society groups has published new research showing that there have been just 450 female MPs in Britain’s history, which is less than the number of male MPs currently sitting in the Commons.

The report, Sex and Power, by the Centre for Women & Democracy, Electoral Reform Society, Unlock Democracy, Fawcett Society and the Hansard Society, found that women made up just 26% of all candidates at the last election, with the Greens, Labour and the SNP having the most at 37%, 36% and 33% respectively, while just 12% of Ukip candidates were female.

It also found that women make up just under a third (32%) of cabinet members, and 24% of junior government posts.